Synthesis, calcination and characterization of Nanosized ceria powders by self-propagating room temperature method

Abstract

Nanometric ceria powders with fluorite-type structure were obtained by applying self-propagating room temperature method. The obtained powders were subsequently thermally treated (calcined) at different temperatures for different times. Powder properties such as specific surface area, crystallite size, particle size and lattice parameter have been studied. Roentgen diffraction analysis (XRD), BET and Raman scattering measurements were used to characterize the as-obtained (uncalcined) powder as well as powders calcined at different temperatures. It was found that the average diameter of the as-obtained crystallites is in the range of 3-5 nm whereas the specific surface area is about 70 m(2)/g. The subsequent, 15 min long, calcination of as-obtained powder at different temperatures gradually increased crystallite size up to similar to 60 nm and reduced specific surface down to 6 m(2)/g. Raman spectra of synthesized CeO2-y depicts a strong red shift of active triply degenerate F-2 (g) mode as well as additional peak at 600 cm(-1). The frequency of F-2 g mode increased while its line width decreased with an increase in calcination temperature. Such a behavior is considered to be the result of particle size increase and agglomeration during the calcination. After the heat treatment at 800 degrees C crystallite size reached value larger than 50 nm. Second order Raman mode, which originates from intrinsic oxygen vacancies, disappeared after calcination. (c) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.